1. Field of the Invention
The invention relates to a throat closing device for shaft furnaces, in particular, blast furnaces with a material feeding hopper to which is connected a temporarily rotating rotary hopper sealed relative to the stationary parts.
2. Description of the Related Art
For filling in and distributing charges for burdening shaft furnaces, devices have been known for a long time which are configured according to the so-called McKee principle. In this configurationxe2x80x94a bell-type throat closing devicexe2x80x94in the upper part a xe2x80x9csmall bellxe2x80x9d and in the lower part a xe2x80x9clarge bellxe2x80x9d are arranged. In this connection, the upper one of the stacked bells or hoppers is rotatable.
A further development of the McKee-type throat closing device resides in that the lower large bell must not form a gas-tight closure because the rotary distributing hopper closed by the bell is arranged in a seal-tight enclosure.
In an arrangement known from DE 36 32 724 C2 the problem of providing a seal between the lower distributing bell and the lower lock chamber is solved in that the upper hopper is formed as a pressure-tight closeable lock chamber by means of a stationary hood provided with burdening flaps.
From DE-AS 10 13 681 a sealing device on rotatable throat closing devices of blast furnaces is known, comprising a pressure ring fastened on the rotary hopper and a matching stationary annular sealing mass, wherein the sealing action of the pressure ring and sealing mass is realized by a spring force. In an annular housing, which is fastened in a gas-tight way on the throat hood, adjustable springs are arranged for this purpose which continuously press the sealing mass onto the sliding ring rotating with the rotary hopper. The pressing force of the springs can be variably adjusted by a clamping device comprised of a readjustable clamping screw.
In further known burdening devices for blast furnaces, for example, according to DE 20 35 458, DE 20 65 460, which are operated at the throat with counterpressure, a stationary central material inlet is provided via which the burden falls onto a rotary chute. The rotary support and the drive parts of the chute are located in the furnace space. This latter described feeding device has also been improved in many ways. For example, the rotary support and the drive parts of the chute have been arranged in their own housing which is separate from the remaining furnace space. A flushing gas inlet opens into the aforementioned housing. This is designed to prevent that hot and dust-laden blast furnace gases can enter.
For supplying material in order to operate a shaft furnace, different types of burdening devices are known. For example, a rotary hopper which is driven by a crown gear is used in a bell-type closure for uniform material distribution. The inner space of the rotating hopper is located in the direct surroundings of the furnace space, i.e., the space is exposed to the furnace atmosphere. For this reason, sealing of the rotating part of the hopper relative to the surroundings is necessary. The sealing action is realized by means of a labyrinth seal by using spring-loaded graphite rings, preferably composed of segments connected by tongue and groove connections which provide sealing in an N2 atmosphere. The N2 atmosphere must be regulated relative to the furnace pressure so that a slight overpressure relative to the furnace pressure is present. Nitrogen is moreover a gas which is very expensive.
It is an object of the invention to provide a throat closing device of this kind without the aforementioned disadvantages, wherein, at the same time, it should be of a constructively simpler configuration and more assembly-friendly as well as have good servicing possibilities.
This object is solved according to the invention by a sealing unit comprised of a liftable and lowerable adjustable flange arranged above the rotary hopper and complementary to its hopper flange and having seals at the flange underside and being provided with a compensation element on the bridging wall connecting the adjusting flange with the stationary part of the rotary hopper. The compensation element, advantageously, for example, in the form of a loop-like strip configuration or the like, can be configured such that, for example, an axial movement of approximately 50 mm, a lateral movement of approximately 20 mm, as well as an overpressure of 3.5 bar can be received. The system can be controlled such that during the material supply from the receiving hopper into the space xe2x80x9csmall bellxe2x80x9d the adjusting flange is lifted. Subsequent to supplying the material, the rotary hopper can rotate for the purpose of material distribution. Before emptying the space xe2x80x9csmall bellxe2x80x9d into the space xe2x80x9clarge bellxe2x80x9d, the adjusting flange is lowered so that the parts are sealed relative to one another; this makes it possible to perform a required pressure compensation. The deformable compensation element which makes possible the movement play is moreover able to compensate a possible displacement relative to the axis of rotation. Moreover, a nitrogen atmosphere is not needed in order to generate a slight overpressure relative to the furnace pressure. The entire sealing unit or the sealing system is easily accessible from the exterior and, moreover, enables assembly on site.
According to a preferred embodiment of the invention, lifting cylinders connected to the adjusting flange are arranged in a distributed fashion on the periphery of the stationary part of the rotary hopper and attached thereto. These hydraulic cylinders take over not only lifting and lowering and thus venting of the adjusting flange during feeding of the material, but can also provide a securing force which must only be so great that lifting off of the sealing unit as a result of the force of the inner pressure of the shaft furnace is prevented.
According to a suggestion of the invention the adjusting flange has two spaced apart annular seals of which the forward annular seal neighboring the axis of rotation of the rotary hopper is formed as a seal preventing dust from exiting when the adjusting flange is lifted. During material supply the outer annular seal, which is moved toward the end face of the adjusting flange, is not active in the lifted position of the adjusting flange, i.e., it is not in an engaged position. On the other hand, the forward annular seal closer to the axis of rotation prevents even in the vented operating position of the adjusting flange the dust from exiting. Before emptying the space xe2x80x9csmall bellxe2x80x9d into the space xe2x80x9clarge bellxe2x80x9d, the cylinders are moved so that a sealing action of the parts for performing the required pressure compensation takes place. During the course of lowering of the adjusting flange approaching increasingly the hopper flange, the dust particles lying on the counter surfaces are engaged by the annular seal via the sealing edges of the annular seal and moved so that a substantially dust-free sealing surface results.
One embodiment of the invention suggests that between the rotary hopper flange and the adjusting flange a stop is arranged. This stop which is fastened, preferably adjustably, on the rotary hopper flange prevents impermissible pressing of the seals. The adjustability makes it possible to compensate a possible seal wear.
According to the invention it is furthermore suggested to provide a gliding skirt upstream of the compensation element relative to the furnace or hopper interior which skirt is secured with only one end on the bridging wall and rests with the other end loosely on the bridging wall. Accordingly, a skirt is thus provided at the compensation element which provides reinforcement in the direction toward the pressure area and which, as a result of its loose arrangement on one side, can glide with its free end across the bridging wall upon lifting movements of the adjusting flange.